electrolysis question gcse

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jennaa21
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#1
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how do i know when water is being produced at the anode ?
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kcamiii
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(Original post by jennaa21)
how do i know when water is being produced at the anode ?
its not i think
aqueous solution - hydroxide ions and hydrogen ions present
at anode, hydroxide ions are attracted and oxygen is produced (not water) but this is only if there aren't any halide ions present in solution
^that's what i can remember off the top of my head, maybe watch a cognito vid on electrolysis just to check
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jennaa21
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(Original post by kcamiii)
its not i think
aqueous solution - hydroxide ions and hydrogen ions present
at anode, hydroxide ions are attracted and oxygen is produced (not water) but this is only if there aren't any halide ions present in solution
^that's what i can remember off the top of my head, maybe watch a cognito vid on electrolysis just to check
im not really sure because i just did a past paper and the reaction was silver nitrate and it asked what the product at anode is and i put oxygen but apparently its oxygen AND water and i wasnt aware of this
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kcamiii
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(Original post by jennaa21)
im not really sure because i just did a past paper and the reaction was silver nitrate and it asked what the product at anode is and i put oxygen but apparently its oxygen AND water and i wasnt aware of this
which paper was this
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dahlia06
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(Original post by kcamiii)
its not i think
aqueous solution - hydroxide ions and hydrogen ions present
at anode, hydroxide ions are attracted and oxygen is produced (not water) but this is only if there aren't any halide ions present in solution
^that's what i can remember off the top of my head, maybe watch a cognito vid on electrolysis just to check
yh i think you're right
chemistry paper 1 in four days...
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kcamiii
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(Original post by jennaa21)
im not really sure because i just did a past paper and the reaction was silver nitrate and it asked what the product at anode is and i put oxygen but apparently its oxygen AND water and i wasnt aware of this
maybe its cus silver isnt very reactive, it wont react with the hydroxide ions and so water is produced?
eg) if there was Na+ ions in solution, NaOH would be produced
not too sure if im honest
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jennaa21
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(Original post by kcamiii)
which paper was this
wait it wasnt a past paper but it was a practice exam paper by CGP and the solutions it said water is produced as well due the aqueous solution also containing water
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kcamiii
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(Original post by jennaa21)
wait it wasnt a past paper but it was a practice exam paper by CGP and the solutions it said water is produced as well due the aqueous solution also containing water
ahh okay. i think the best thing to do would be to just ignore it lol. im pretty sure that past paper answers have never actually included water itself as being produced at the anode. might be useful just to check some electrolysis questions from past papers and compare with the mark scheme. i did them a while back (need to do them again) but i dont remember seeing anything like that. hope this helped, ik my replies were kinda slow tho aha
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lizz-ie
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(Original post by jennaa21)
im not really sure because i just did a past paper and the reaction was silver nitrate and it asked what the product at anode is and i put oxygen but apparently its oxygen AND water and i wasnt aware of this
If you have silver nitrate solution,
CATHODE: ions present are silver (I) (Ag+) and hydrogen (H+). Since silver is less reactive than hydrogen, silver ions gain electrons to produce silver at the cathode, and solid silver is plated on the cathode. Ag+ + e- -> Ag
ANODE: ions present are nitrate (NO3-) and hydroxide (OH-). Hydroxide ions are preferentially discharged in a reaction that produces oxygen, water and electrons. The water will remain in the solution and oxygen will be effervesced from the anode. Half equation is 4OH- -> 2H2O + O2 + 4e-

So, silver ions are discharged as silver metal, hydroxide ions are discharged as oxygen (and water), and the solution following electrolysis will be dilute nitric acid (HNO3) from the remaining ions in solution.
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jennaa21
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(Original post by lizz-ie)
If you have silver nitrate solution,
CATHODE: ions present are silver (I) (Ag+) and hydrogen (H+). Since silver is less reactive than hydrogen, silver ions gain electrons to produce silver at the cathode, and solid silver is plated on the cathode. Ag+ + e- -> Ag
ANODE: ions present are nitrate (NO3-) and hydroxide (OH-). Hydroxide ions are preferentially discharged in a reaction that produces oxygen, water and electrons. The water will remain in the solution and oxygen will be effervesced from the anode. Half equation is 4OH- -> 2H2O + O2 + 4e-

So, silver ions are discharged as silver metal, hydroxide ions are discharged as oxygen (and water), and the solution following electrolysis will be dilute nitric acid (HNO3) from the remaining ions in solution.
thank you sm <3 so in my exam should i say and water or should i just put oxygen if its one mark
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lizz-ie
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(Original post by jennaa21)
thank you sm <3 so in my exam should i say and water or should i just put oxygen if its one mark
Most Edexcel mark schemes say "hydroxide ions are discharged as oxygen gas" and you aren't normally expected to write about the water. You just need to know that the resulting solution is dilute due to the production of water when hydroxide ions are discharged.
I believe AQA have similar mark schemes but can't remember since I'm not teaching that currently!
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scimus63
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try looking here it might help answer your question, good luck in your exam!

https://science-revision.co.uk/elect...20heading.html
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